Figure 6: GLP-1 prevents MG-induced apoptosis of INS-1 and MIN6 cells in part through PKA and PI3 kinase pathway, and partially via improving mitochondrial function and suppressing prolonged AMPK activation.

INS-1 and MIN6 cells were seeded overnight, and then were incubated with indicated treatment for indicated time. (A) INS-1 and MIN6 cells were treated in the absence of MG, 1 mM MG, 1 mM MG + 300 nM GLP-1, 1 mM MG + 300 nM GLP-1 + 100 μM Rp-cAMP, 1 mM MG + 300 nM GLP-1 + 10 μM H-89, 1 mM MG + 300 nM GLP-1 + 30 μM LY294002, 1 mM MG + 300 nM GLP-1 + 50 nM wortmannin, respectively. Cell viability was measured by MTT assay. Data are shown as relative cell viability (mean % ± S.E. bar) as compared with that in control (n = 3). *p < 0.05. (B) INS-1 and MIN6 cells were treated with or without 1 mM MG in the presence or absence of 300 nM GLP-1 for 1 hr, 2 hr, 4 hr, 6 hr, and 17 hr, respectively. Relative intracellular ATP concentration (%) compared with control in indicated time (n = 3). *p < 0.05 (Control vs. 1 mM MG at 1 hr, 2 hr, 4 hr, 6 hr and 17 hr), #p < 0.05 (1 mM MG vs. 1 mM MG + 300 nM GLP-1 at 1, 6, and 17 hr in INS-1 cells; 1, 4, 6, and 17 hr in MIN6 cells). (C) INS-1 and MIN6 were treated by 1 mM MG with or without GLP-1 for 0, 2, 4, 6, and 17 hr. Western blot of PARP, pAMPK/AMPK, and GAPDH was used as internal control. (D) INS-1 and MIN6 cells were treated in the absence or presence of 1 mM MG with or without 10 μM compound C (C.C.) for 17 hr. Cell viability was measured by MTT assay. Data are shown as relative cell viability (mean % ± S.E. bar) as compared with that in control (n = 3). *p < 0.05. (E) INS-1 and MIN6 cells were treated in the absence of 1 mM MG or 1.5 mM AICAR, 1 mM MG, 1.5 mM AICAR, 1 mM MG + 300 nM GLP-1, 1.5 mM AICAR + 300 nM GLP-1, 1 mM MG + 100 μM metformin for 17 hr, respectively. Cell viability was measured by MTT assay. Data are shown as relative cell viability (mean % ± S.E. bar) as compared with that in control (n = 3). *p < 0.05.